Cascading optical switch three dimensional switch fabric system and method

ABSTRACT

The present invention cascaded optical switching system includes architectures that provide three dimensional optical signal beam steering utilizing two dimension optical signal beam steering devices. A plurality of cascaded optical switches form a cascaded multi-dimensional optical switch fabric and direct an optical signal beam from one of the plurality of optical switches to another of the plurality of optical switches in a different dimension. In one embodiment, an incidence corrective device is included in a cascaded optical switch fabric and directs an optical signal beam in a shallow angle so that it strikes the next optical switch at a corrected incidence angle. A corrected incidence angle permits an optical signal beam to be forwarded at a relatively shallow angle to an optical switch located in a relatively close proximity on the optical switch fabric. The present invention also provides for refocusing of spreading optical signal beams and mitigation of signal loss.

FIELD OF THE INVENTION

The present invention relates to the field of optical signal beammanipulation and propagation. More particularly, the present inventionrelates to a system and method to facilitate multi-dimensional cascadedswitching of optical signal beams with viable incidence angle correctionand beam spread correction.

BACKGROUND OF THE INVENTION

Systems utilizing various types of signals to represent information havemade a significant contribution towards the advancement of modernsociety and are utilized in a number of applications to achieveadvantageous results. Numerous technologies such as digital computers,calculators, audio devices, video equipment, and telephone systemsfacilitate increased productivity and cost reduction in analyzing andcommunicating information in most areas of business, science, educationand entertainment. Advanced optical signal based technologies offer thepotential for rapid processing and communication of large amounts ofdata associated with a variety of activities. The optical based systemstypically involve signal manipulation by signal switching operations.However, a number of optical signal beam manipulation problemsassociated with achieving optimal incidence angles and/or minimaloptical signal beam spreading often make traditional control of thesignals difficult or impractical.

To obtain maximized performance from information systems it is usuallycritical for the information to be processed and communicated rapidlyand reliably. Encoding information in optical signals offers thepotential for manipulation and conveyance of significant amounts ofinformation very quickly. For example, most optical systems havesignificant potential bandwidth capacity for processing andcommunicating a large quantity of data per unit of time. While sometypes of optical signal beam controls are relatively simple and easy toaccomplish such as transmission of an optical signal beam along aconfined single waveguide path (e.g., formed by a fiber optic cablestrand), other types of optical signal beam control such as dynamicallydirecting an optical signal beam along various paths are relativelydifficult.

The ability to control the manipulation and propagation of opticalsignal beams through a variety of paths usually involves theimplementation of switching elements. Switching elements provide amechanism for directing the optical signal beam to a particulardestination, often redirecting the signals along particular designatedpaths. However, the resources involved in manufacturing attempts at asingle switch capable of redirecting optical signals goes up as thenumber of potential paths increase. Some traditional switching networksystem configurations attempt to forward a signal to multiple potentialdestinations by utilizing a network of discrete limited switchesconnected with external cabling. These traditional attempts typicallyconsume significant resources to manufacture each discrete switch oflimited capability and additional resources to “wire” them together(e.g., connect cables between each individual limited switch). Anothertraditional approach to switching operations involves converting anoptical signal into an electrical signal and vise versa. Theseapproaches are usually slow and require significant resources toimplement.

Switching optical signal beams typically involves significant challengesfor single switches capable of directing optical signal beams along avariety of paths. The nature of light propagation gives rise to a numberof complications that can potentially limit or impede the ability todirect an optical signal beam to a particular destination. Cumulativedetrimental effects associated with repeated redirection of opticalsignals tend to limit the practical utilization of traditional opticalswitches for applications involving significant control flexibility. Therelationship of incidence angles and output angles can give rise todetrimental effects in situations where angles become cumulativelydeeper each time an optical switch redirects an optical signal beam.Large incidence angles often prevent the propagation of an opticalsignal beam to a nearby device at an optimal incidence angle. Anotherpotential detrimental impact of repeated redirection of an opticalsignal beam is deteriorating divergence or spread of the optical signalbeam. Each time an optical beam is switched it spreads and a portion ofthe signal energy is lost. Theses energy losses are typically cumulativeand have adverse impacts on interpreting the weakened signals.

SUMMARY

The present invention is a system and method that facilitates efficientoptical signal beam switching. A present invention cascaded opticalswitching system includes architectures that provide three dimensionaloptical signal beam steering utilizing two dimension optical signal beamsteering devices (e.g., two dimensional optical switches). Thearchitectures facilitate redirection of an optical signal beam alongpaths in three different dimensional planes. In one embodiment of thepresent invention, the propagation of optical signal beams alongdifferent planes permits greater switching flexibility along shortermulti-dimensional cascading switch fabrics. The present inventionmulti-dimensional cascaded optical switching system and methodfacilitates flexible high density switching configurations by permittingnumerous switches to be arranged in close proximity to one another inmultiple dimensions with each dimension providing a variety of differentswitching routes.

In one embodiment, a cascaded optical switch fabric includes a pluralityof cascaded optical switches arranged in multiple stages and are coupledto optical switch support members separated by a bracing member. Theplurality of cascaded optical switches form a cascaded optical switchfabric and a multi-dimensional directional device directs an opticalsignal beam from one of the plurality of optical switches to another ofthe plurality of optical switches in a different dimensional stage orplane. The optical switch support members support the plurality ofcascaded optical switches in a cascaded configuration across multiplestages in different planes. The bracing member holds the optical switchsupport members in a position relative to one another and forms acascaded optical switch fabric. In one embodiment of the presentinvention, a multi-dimensional directional device is included in acascaded optical switch fabric stage and directs a signal to anotheroptical switch fabric stage in a different plane (e.g., amulti-dimensional directional device directs an optical signal beam froma first optical switch stage to a second optical switch stage orientedin a different dimensional plane).

In one exemplary implementation, the optical signal beam is directedthrough “free-space” (e.g., air or glass not confined by a waveguide) bycascaded switching elements. The present invention cascaded opticalswitching system and method facilitates minimization of cumulativedetrimental impacts associated with cascaded switching of optical signalbeam. For example, a present invention cascaded optical switching systemcan “regenerate” an optical signal beam path with a realigned orcorrected incidence angle. A corrected incidence angle permits anoptical signal beam to be forwarded at a relatively shallow output angleto an optical switch located in a relatively close proximity on thecascading optical switch fabric. In one embodiment of the presentinvention, the corrected incidence angle facilitates shortening thecascaded switch fabric length. In one exemplary implementation, apresent invention cascaded optical switching system refocuses opticalsignal beams mitigating adverse impacts (e.g., energy loss) associatedwith diverging or spreading beams.

DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram of a invention cascaded optical switchingsystem in accordance with one embodiment of the present invention.

FIG. 1B is a different block diagram view of cascaded optical switchingsystem in accordance with one embodiment of the present invention.

FIG. 1C is a block diagram view of one exemplary cascaded opticalswitching system from another axis perspective.

FIG. 1D is a three dimensional view of one embodiment of a cascadedoptical switching system.

FIG. 1E is a block diagram of an alternate embodiment in which theoptical switches (e.g., dynamically variable optical switches 181, 182and 183) are mounted on the surface of a single substrate 189.

FIG. 2 is a block diagram section of cascaded optical switching systemin which an optical signal beam is forwarded in two different spatialplanes.

FIG. 3A is a block diagram illustration of cascaded optical switchingsystem, one embodiment of the present invention in which multipleoptical signal channels are switched simultaneously.

FIG. 3B is a block diagram of one embodiment of an optical cross connectsystem including a present invention cascaded optical switching system.

FIG. 4A is a three dimensional block diagram of a dynamically variablegrating based optical switch included in one embodiment of the presentinvention.

FIG. 4B shows a cross section side view block diagram of grating from anoptical switch.

FIG. 4C illustrates a three dimensional cut-away view of the opticalswitch where the grating is shown with alternating ribbons in adeflected position relative to undeflected ribbons in accordance withone two level grating embodiment of the invention.

FIG. 4D is a block diagram illustration of a variety of two levelconfigurations for a dynamically variable grating based optical switch.

FIG. 4E is a block diagram illustration of a variety of blaze patternsfor a dynamically variable grating based optical switch.

FIG. 4F is a three dimensional block diagram of one embodiment of thepresent invention in which dynamically variable grating based opticalswitches are included in cascading topical switch fabric.

FIG. 5 is a block diagram illustration of cascaded optical switchingsystem, one embodiment of the present invention with a fixed incidenceangle regeneration device.

FIG. 6 is a three dimensional representation of a cascaded opticalswitching system with a fixed incidence angle regeneration device.

FIG. 7A is a block diagram illustration of cascaded optical switchingsystem, one embodiment of the present invention with a dynamicallyvariable incidence angle regeneration device.

FIG. 7B is a three dimensional block diagram illustration of cascadedoptical switching system, one embodiment of the present invention with adynamically variable incidence angle regeneration device.

FIG. 8A is a three dimensional block diagram of a fixed angle incidencecorrective device that also provides optical signal spread beamcorrection, one embodiment of the present invention.

FIG. 8B is a three dimensional block diagram of a dynamically variableand incidence corrective device that also provides optical signal beamspread correction, one embodiment of the present invention.

FIG. 9 is a flow chart of a cascaded optical switching method, oneembodiment of the present invention.

DETAILED DESCRIPTION

Reference will now be made in detail to the preferred embodiments of theinvention, a cascading optical three dimensional switch fabric systemand method, examples of which are illustrated in the accompanyingdrawings. While the invention will be described in conjunction with thepreferred embodiments, it will be understood that they are not intendedto limit the invention to these embodiments. On the contrary, theinvention is intended to cover alternatives, modifications andequivalents, which may be included within the spirit and scope of theinvention as defined by the appended claims. Furthermore, in thefollowing detailed description of the present invention, numerousspecific details are set forth in order to provide a thoroughunderstanding of the present invention. However, it will be obvious toone ordinarily skilled in the art that the present invention may bepracticed without these specific details. In other instances, well knownmethods, procedures, components, and circuits have not been described indetail as not to unnecessarily obscure aspects of the current invention.

FIG. 1A is a side view and FIG. 1B is a top view block diagram ofcascaded optical switching system 100, one embodiment of the presentinvention. Cascaded optical switching system 100 includes opticalswitches (e.g., S01, S103, S303, S503, S703) and dimensional directionaldevices M100 through M740 and optical switch support members 111 and112. In one embodiment, optical switch support member 112 is coupled tooptical switches S01 through S743, and optical switch support member 111is coupled to multi-dimensional directional devices M100 through M740.Thus, the present invention permits the overall length of the switchfabric to be shortened because devices are arranged “beside” each otherin multiple directions. In one embodiment of the present invention, theoptical switches and multi-dimensional devices are coupled to supportmembers 111 and 112 in a cascaded multi-dimensional pattern. In oneembodiment of the present invention, the optical switch support membersare reflective optical switch fabric boundary planes coupled to eachother by position bracing members (not shown) that hold the opticalswitch support members in a position relative to one another.

The designation of a component as an optical switch or amulti-dimensional directional device is based upon the primary functionthe component provides. For example, an optical switch primarily directsthe light in a single plane (e.g., a plane formed by the Z and X axis)and a multi-dimensional device primarily directs light between planes(e.g., directs the light from a first plane formed by the Z and X axisto a second plane formed by the Z and Y axis).

It is appreciated that embodiments of the present invention are wellsuited for use with a variety of different types of components. In oneembodiment of the present invention, optical switches andmulti-dimensional directional devices include a reflective component andin another they include a diffractive component. For example, thediffractive components facilitate easier semiconductor manufacturingprocesses and the reflective components facilitate easier opticalmanufacturing processes. The reflective components and diffractivecomponents may be fixed (e.g., direct an optical signal beam at aparticular output angle for a given input angle) or dynamically variable(e.g., direct an optical signal beam at variable output angles for agiven input angle). In an alternative embodiment, one exemplaryimplementation the multi-directional devices are fixed reflectivedevices or fixed diffractive devices (e.g., a fixed grating). In oneimplementation, a multi-dimensional directional device comprises a fixedreflective surface oriented at a particular angle to guide said opticalsignal beam to said different plane. For example, a pair of fixedmirrors or fixed gratings oriented to direct the optical signal beambetween planes. In one exemplary implementation, the angled mirrors(e.g., angled at less than 45 degrees) are fabricated on silicon usingKOH etch yielding 33 degree angle to the mirrors. In yet anotherembodiment of the present invention, the optical switches andmulti-dimensional directional devices include a variable diffractioncomponent (e.g. a dynamically variable grating based switch). In oneexemplary implementation, the optical switches are grated light valve(GLV) switches. In some exemplary implementations, a combination ofdifferent types of components are included in the switch fabric.

FIG. 1B is a different block diagram view of cascaded optical switchingsystem 100, one embodiment of the present invention. FIG. 1B illustratesthe cascaded optical switch stages formed in different dimensions.Multi-dimensional directional devices M100, M300, M500 and M700 redirectan optical signal beam from a stage in a first dimension to anotherstage in a different dimension and the remaining multi-dimensionaldirectional devices receive the optical signal beam from the firstdimension and pass it along their respective optical switch fabricstages. For example, an optical signal beam is directed frommulti-dimensional devices M100 to switch S103 in a first dimension whichredirects the optical signal beams to multi-dimensional directionaldevices M110, M120, M130 or M140 in a second dimension which in turndirect the optical beam to switch S113, S123, S133 or S143 respectivelyin a second dimension. FIG. 1C is a block diagram view of cascadedoptical switching system 100 from another axis perspective. Figure D isa three dimensional view of one embodiment of cascaded optical switchingsystem 100.

The components of cascaded optical switching system 100 cooperativelyoperate to direct the propagation of an optical signal beam thoughcascaded optical switching system 100. In one embodiment, cascadedoptical switching system 100 is configured in an architectures thatenables three dimensional multi-dimensional optical signal beam steeringutilizing two dimension optical signal beam steering devices. Forexample, two dimensional optical switches and two dimensionalmulti-dimensional devices that individually direct the optical signalbeam in two dimensions but when combined in a present inventionarchitecture facilitate three dimensional optical signal beam steering.In one exemplary implementation, the optical signal beam is directedthrough “free-space” (e.g., air or glass not confined by a waveguide) bycascaded switching elements. In one exemplary implementation of thepresent invention, an optical signal beam enters a present inventioncascading optical switch fabric and is directed along the cascadedoptical switches to another receiver or path (e.g., to a waveguide suchas an optical cable or other optical device).

In embodiment of the present invention, the optical switches arearranged in cascaded switching stages in which each stage includes aplurality of optical devices. For example, optical switches S01, S103,S303, S503, S703 form a first stage and optical switches S113, S123,S133 and S143 form a second stage. In one embodiment of the presentinvention, the optical switch support members 111 and 112 are cascade“boundary” planes coupled to each other by position bracing members (notshown) that hold the optical switch support members in a positionrelative to one another. In one embodiment of the present invention,optical switch support members 111 and 112 are surfaces of a singlesubstrate 188 (e.g., a free space such as glass) and the opticalswitches are mounted in the substrate 188. FIG. 1E is a block diagram ofan alternate embodiment in which the optical switches (e.g., dynamicallyvariable optical switches 181, 182 and 183) are mounted on the surfaceof a single substrate 189. In exemplary implementation a plane (e.g., asupport member 111 or surface of a substrate) include passive elements(e.g., passive mirrors) and an opposite plane (e.g., support member 122or opposite substrate surface) include active elements (e.g., activedynamically variable grating based optical switch).

There are a variety of cascading configuration implementations of thepresent invention cascaded optical switching system 100. In oneembodiment of the present invention, cascaded optical switching system100 directs optical signal beams to a variety of receivers or paths withdifferent spatial orientation. For example, cascaded optical switchingsystem 100 directs optical signal beams to optical switches oriented inthe same dimension or stage or in different spatial dimensions (See FIG.1D). FIG. 2 is a block diagram section of cascaded optical switchingsystem 200 in which an optical signal beam is forwarded in two differentspatial planes. Cascaded optical switching system 200 comprises opticalswitches 220 and 230, optical switch support members 241 and 245,position bracing member 245 and optical waveguide receiver 250. Opticalswitch support member 241 is coupled to optical switch 220 and opticalswitch support member 242 is coupled to optical switch 230. In oneembodiment of the present invention, cascaded optical switching system200 comprises additional optical switches (not shown) upstream anddownstream from optical switches 210 and 230 and position bracing member245 forms a reflective optical switch fabric boundary plane coupled tothe optical switch support members 241 and 242.

The components of cascaded optical switching system 200 cooperativelyoperate to direct the propagation of an optical signal beam thoughcascaded optical switching system 200. FIG. 2 shows optical waveguidereceiver 250 coupled to optical waveguide 251 (e.g., a fiber opticalcable) which is in a different spatial plane than the cascaded opticalswitches of cascaded optical switching system 200. Optical signal beam210 is received by cascaded optical switching system 200 and directed ina cascaded fashion to optical switch 220 which directs it to opticalswitch 230. Optical switch 230 directs optical signal beam 210 tooptical waveguide receiver 250 which forwards the optical signal beam210 to optical waveguide 251 (e.g., fiber optical cable). Opticalwaveguide 251 directs the optical signal beam 210 along a path in aspatial plane different from the cascading plane of cascaded opticalswitching system 200.

A present invention cascaded optical switching system is adaptable tomanipulate and convey a variety of different optical signals in numerousdifferent cascaded configurations. For example, a present inventioncascaded optical switching system is capable of handling a plurality ofoptical signals simultaneously. FIG. 3 is a block diagram illustrationof cascaded optical switching system 300, one embodiment of the presentinvention. In one exemplary implementation of the present invention, aplurality of optical signals are communicated in one optical signal beam390 simultaneously to optical switch 310. In one exemplaryimplementation, optical signal beam 390 comprises a plurality of opticalsignals oscillating at different frequencies (e.g., different colors).Optical switch 310 directs the resulting different color optical signalbeams to different receivers or paths. For example, optical signal beam393 oscillating at a first frequency is directed along a first path(e.g., to optical switch 320) and optical signal beam 395 oscillating ata second frequency is directed along a second path (e.g., to opticalswitch 330). Directing the two optical signal beams along differentpaths facilitates different manipulation and conveyance of the signalssimultaneously. For example, optical signal beam 393 could be directedby optical switch 320 to optical waveguide 375 and optical signal beam395 could be directed by optical switch 330 along the optical switchfabric to other downstream optical switches (not shown).

In one exemplary implementation of the present invention, a reflectiveswitch is included in the cascaded optical switch fabric. In oneembodiment of the present invention, the reflective switch has areflective mirror surface and the direction it is pointing is adjustableto reflect the optical signal light beam in a different direction. Forexample, an optical signal beam hits the reflective surface at aparticular incidence angle and is reflected to a second destination(e.g., a second reflective switch included in the cascaded opticalswitch fabric). The direction the reflective surface is pointing isaltered (e.g., a mirror rotating on an axis) and the optical switchlight beam is reflected to a second destination (e.g., a thirdreflective switch included in the cascaded optical switch fabric).

A present invention cascaded optical switching system is readilyadaptable to provide a variety of functions. FIG. 3B is a block diagramof one embodiment of an optical cross connect system 390 comprising apresent invention cascaded optical switching system. In one exemplaryimplementation, an optical signal beam is directed into optical crossconnect system 390 on a fiber cable (e.g., fiber 1, fiber 2, . . . fiberN) and is directed out on another one of the fiber cables (e.g., fiber1, fiber 2, . . . fiber N).

FIG. 4A is a three dimensional block diagram of dynamically variablegrating based optical switch 10, one example of a dynamically variablegrating based optical switch. Dynamically variable grating based opticalswitch 10 is included in one embodiment of the present invention andincludes ribbon micro electromechanical machines (MEMs). In oneexemplary implementation of the present invention, dynamically variablegrating based optical switch 10 is a grating light valve switch.Dynamically variable grating based optical switch 10 utilizesdiffraction to control the direction of an optical signal. Thediffraction grating of dynamically variable grating based optical switch10 comprises multiple ribbons 30 supported in a position relative to oneanother. In one exemplary implementation multiple ribbons 30 aresupported by an integrally attached support base 20.

FIG. 4B shows a cross section side view block diagram of an exemplarygrating included in one embodiment of dynamically variable grating basedoptical switch 10. In one exemplary implementation of the presentinvention, each ribbon 30 includes a reflective planar surface 35. Theribbons of the grating are easily arranged in a variety ofconfigurations. For example, the ribbons can be arranged in a two levelpattern (e.g., can be a square well or other two level pattern), a blazepattern, a step blaze pattern, a sinusoidal pattern, a triangularpattern, a combination of patterns, etc. The ribbons of grating arearranged in a single planar configuration in FIG. 4A and FIG. 4B. FIG.4C illustrates a three dimensional cut-away view of the optical switchwhere the grating is shown with alternating ribbons in a deflectedposition relative to undeflected ribbons in accordance with one twolevel embodiment of the invention (e.g., forming a square well patternswitch). A two level ribbon arrangement is one in which each ribbon islocated in one of two plans. FIG. 4D is a block diagram illustration ofa variety of two level configurations 471, 472, 473, and 474. FIG. 4E isa block diagram illustration of blaze patterns 491 and 492.

In one embodiment of the present invention, the ribbons are dynamicallyvaried. In one exemplary implementation of the present invention, theribbons are dynamically varied by selectively introducingelectromagnetic fields that deflect the ribbons. For example, amechanism for applying an electrostatic force between each ribbon andsupport base 20 is included. The position of the deflected ribbon iscontrolled by varying the strength of the applied electric field. Otherways or mechanisms for moving the ribbons relative to one another couldbe employed. In one exemplary implementation, the ribbons are supportedon their ends by slide supports which allow the ribbons to move as rigidbodies with minimal ribbon end deformation.

The configuration style and arrangement of the ribbons govern thediffraction angle of an optical signal beam. In one exemplaryimplementation of the present invention, mathematical formulas utilizedto express the behavior of a diffracted signal beam define the differentresults that are achievable with different configuration styles andarrangements. For example, the diffraction of an optical signal beam byone configuration of a two level optical switch (e.g., forming a squarewell pattern) is governed by the equations:

-   -   P=n(W+S), where P is the period or pitch, n is the number of        ribbons utilized in forming a single grating period, W is the        ribbon width, and S is the space between the ribbons; and    -   B=Arcsin ((m*Y*N)±Sin A), where N=1/P or 1/(n(W+S)), B is the        diffraction angle, A is an optical signal impingement or        incidence angle, m is the order of the diffraction beam and Y is        the wavelength of the optical signal.        One example of an optical signal beam diffraction by a blaze        ribbon configuration pattern is defined by the equation:        B=Arcsin((m*Y*N)±sin A), where N=1/P.        For any given A and Y, the value of B can be altered for a given        order by controlling N which is done by deflecting the ribbons        and manipulating the grating period or pitch (e.g., the number        of ribbons in a period). Different ribbon deflection        configurations result in different optical signal beam        diffractions.

FIG. 4F is a three dimensional block diagram of one embodiment of thepresent invention in which dynamically variable grating based opticalswitches are included in cascading optical switch fabric. Cascadedoptical switching system 400 comprises dynamically variable gratingbased optical switches 420, 430 and 435, and optical switch supportmembers 441 and 445. Optical switch support member 441 is coupled tooptical switch 420 and optical switch support member 442 is coupled tooptical switch 430 and 435. In one embodiment of the present invention,cascaded optical switching system 400 comprises additional opticalswitches (not shown) upstream and downstream from optical switches 410and 435.

Some embodiments of a present invention cascaded optical switchingsystem facilitate optical signal beam incidence angle “correction” orrealignment. The corrected incidence angle enables a plurality ofoptical switches to be cascaded in a relatively short configuration. Forexample, the corrected incidence angle is a normal (zero) incidenceangle or near normal incidence angle in some implementations of thepresent invention. The present invention cascaded optical switchingsystem utilizes an incidence corrective device to realign the incidenceangle to produce a relatively shallow output angle. The shallow outputangle directs the optical signal beam on a path to a close opticalswitch included in the cascaded optical switch fabric.

FIG. 5 is a block diagram illustration of cascaded optical switchingsystem 500, one embodiment of the present invention with a fixedincidence angle regeneration device. Cascaded optical switching system500 includes optical switches 521, 531, 532, 541, 542, 551, 552, 571,572, 581 and 582, optical switch support members 511 and 512, andincidence corrective device 585. Optical switch support member 511 iscoupled to optical switches 531, 532, 551, 552, 581 and 582 and opticalswitch support member 512 is coupled to incidence corrective device 585and optical switches 521, 541, 542, 571, and 572. The optical switchesand optical switch support members of cascaded optical switching system500 are similar to those in cascaded optical switching system 100. Theincidence corrective device 585 receives an optical signal beam from anoptical switch (e.g., optical switch 551) at a first incidence angle anddirects it at a second output angle that is shallower than the firstincidence angle.

In one embodiment of the present invention, the incidence correctivedevice 585 directs the optical signal beam at an angle that leads it ona path normal to the base of corrective device 585 coupled to opticalswitch support member 512. In one exemplary implementation of thepresent invention, the incidence corrective device 585 directs theoptical signal beam at an angle that leads it on a path normal to anoptical switch (e.g., optical switch 581) and thereby regenerates a zeroangle of incidence at the optical switch. This enables downstreamoptical switches (e.g., optical switches 571 and 582) to be placed incloser proximity to one another in the cascaded optical switch fabric.

A present invention incidence corrective device has a number ofconfigurations and is flexibly adaptable to a number of differentimplementations. In one embodiment of the present invention, anincidence corrective device includes a fixed reflective componentoriented at a particular angle. In one exemplary implementation of thepresent invention, an incidence corrective device includes a fixedreflective component (e.g., a mirrored surface) oriented at an angledefined by one half the output angle an optical signal beam is forwardedfrom. For example, the reflective component orientation angle ofcorrective device 585 is a half of a first output angle (e.g., thetaminus one) of an optical signal beam from optical switch 551. The“regenerated” or corrected incidence angle (e.g., alpha) at which theoptical signal beam strikes the next optical switch (e.g., opticalswitch 581) is close to zero. The optical signal beam is forwarded at asecond output angle (e.g., theta) that is relatively shallow and permitsthe optical signal beam to travel on a path directed to an opticalswitch (e.g., optical switch 571) located in a relatively closeproximity on the cascading optical switch path. FIG. 6 is a threedimensional representation of a cascaded optical switching system 500with a fixed incidence angle regeneration device. In another embodiment,a fixed incidence angle regeneration device is a fresnel mirror deviceconfigured with concentric fresnel grooves.

FIG. 7A is a block diagram illustration of cascaded optical switchingsystem 700, one embodiment of the present invention with an incidencecorrective device capable of providing dynamically variable incidenceangle regeneration. Cascaded optical switching system 700 includesoptical switches 721, 731, 732, 741, 742, 751, 752, 771, 772, 781 and782, optical switch support members 711 and 712, and incidencecorrective device 787. Optical switch support member 711 is coupled toswitches 731, 732, 751, 752, 781 and 782 and optical switch supportmember 712 is coupled to incidence corrective device 787 and switches721, 741, 742, 771, and 772. The optical switches and optical switchsupport members of cascaded optical switching system 700 are similar tothose in cascaded optical switching system 100. The incidence correctivedevice 787 receives an optical signal beam from an optical switch (e.g.,optical switch 751) at a first incidence angle and directs it at asecond angle that is shallower than the output angle from a previousoptical switch. The output angle of an optical signal beam directed fromincidence corrective device 787 is dynamically variable which permitsflexible control of optical signal propagation and can direct theoptical signal beam so that it strikes a downstream optical switch at acorrected or “regenerated” incidence angle. A corrected or regeneratedincidence angle is one that assists the reduction of cumulativedetrimental effects associated with a deteriorating or deepeningincidence and output angle.

As indicated above, a present invention incidence corrective device hasa number of configurations and is flexibly adaptable to a number ofdifferent implementations. In one of the present invention, an incidencecorrective device is a dynamically variable incidence corrective device.In one exemplary implementation of the present invention, a dynamicallyvariable incidence corrective device includes a variable reflectivecomponent (e.g., a mirrored surface or a reflective optical switch)capable of being oriented or adjusted to point in a variety ofdirections. The corrected or “regenerated” incidence angle (e.g., alpha)at which the optical signal beam strikes the next optical switch isclose to zero. FIG. 7B is a three dimensional block diagram illustrationof cascaded optical switching system 700, one embodiment of the presentinvention with a dynamically variable incidence corrective device. Inone exemplary implementation, the incidence corrective device is adynamically variable grating based optical switch similar to dynamicallyvariable grating based optical switch 10.

In one embodiment, the present invention includes an optical signal beamspread mitigation device in an optical switch fabric. A presentinvention optical signal beam spread correction device corrects beamspreading by refocusing the optical signal beam. Refocusing the opticalsignal beam mitigates signal loss and facilitates efficientinterpretation of signal content.

FIG. 8A is a three dimensional block diagram of a fixed optical signalbeam spread corrective device 810, one embodiment of the presentinvention. Fixed spread corrective device 810 has a concave reflectiveface 811 that reflects the optical signal beam in a focusing pattern. Inone embodiment of the present invention, fixed optical signal beamspread corrective device 810 also reflects the optical signal beam at acorrected incidence angle. For example, an optical signal beam made upof components 821, 822 and 823 are reflected by dual spread andincidence corrective device 810 to a focal point on optical switch 830.By redirecting the components of the optical signal beam towards asingle focal point the optical signal beam is concentrated in a tighterarea. Present invention fixed spread corrective devices have a varietyof reflective face configurations for converging the beam to a tighterfocus (e.g., a concave shaped reflective face, a fresnel mirror, etc.).

FIG. 8B is a three dimensional block diagram of a spread correctivedevice 870, one embodiment of the present invention with dynamicallyvariable spread corrective capabilities that also performs spreadcorrection. Dynamically variable spread corrective device 870 forms achirped reflective face that reflects the optical signal beam in aconverging pattern. In one exemplary implementation, the dynamicallyvariable spread is a dynamically variable grating based optical switch(similar to dynamically variable grating based optical switch 10) andthe ribbons are deflected so that a chirped grating pattern is formed inwhich the periodicity gradually decreases towards the periphery. Thedeflection of the ribbons is dynamically variable and facilitatesflexible control of an optical signal. In one embodiment of the presentinvention, spread corrective device 870 performs dual spread andincidence angle correction functions.

In one embodiment of the present invention, incidence angle correctionand beam spread correction are provided by a single optical device. Inone exemplary implementation, a dual purpose spread and incidencecorrective device corrects incidence degeneration problems byredirecting the focused optical signal beam along a vector that isnormal to the switching stage. For example, spread corrective devices810 and 870 are capable of performing dual spread and incidence anglecorrection functions. In one embodiment of the present invention, a dualpurpose corrective device is included in a cascading optical switchfabric in place of an incidence corrective device (e.g., incidencecorrective device 585 or 787).

FIG. 9 is a flow chart of cascaded optical switching method 900, oneembodiment of the present invention. In one embodiment of the presentinvention, cascaded optical switching method 900 includes an opticalsignal beam incidence angle regeneration process. In one embodiment ofthe present invention, cascaded optical switching method 900 includes anoptical signal beam spread corrective process.

In step 910, an optical signal beam is received by a cascaded opticalswitch fabric. In one exemplary implementation of the present inventionthe optical signal beam is introduced to a cascading optical switchfabric from a waveguide (e.g., a fiber optic cable).

In step 920, the optical signal beam is propagated along the opticalswitch fabric in different dimensions. For example, an optical signalbeam is propagated along the optical switch fabric in stages or planswith different dimensional orientations. In one embodiment of thepresent invention, the optical signal beam is received by a number ofoptical elements (e.g., optical switches, multi dimensional directionaldevice, etc.) and the continued path direction of the optical signalbeam is controlled. In one embodiment of the present invention, theoptical elements are arranged in a cascaded three dimensional order orconfiguration. In one exemplary implementation, optical signals arereceived and forwarded by optical elements. In one embodiment, twodimensional switching elements are combined in a configuration thatprovide three dimensional switching.

In one embodiment, cascaded optical switching method 900 includesdynamically varying the grating pitch within a light diffraction gratingof a dynamically variable grating based optical switch, which in turnvaries the diffraction angle of an optical signal beam switched by thedynamically variable grating based optical switch. In one exemplaryimplementation of the present invention, step 920 includes independentlymoving each ribbon of the dynamically variable grating based opticalswitch in coordination with other ribbons to provide a dynamicallyvarying grating pitch. For example, cascaded optical switching method900 includes applying an electromagnetic field in the proximity of theribbons which causes the ribbons to move (e.g., deflect).

In step 930, the optical signal beam is forwarded away from the opticalswitch fabric. In one embodiment of the present invention, the opticalsignal beam is forwarded to an external waveguide (e.g., a fiber opticcable).

In one embodiment of the present invention, an optical signal beamincidence angle regeneration process forwards the optical signal beams(“regenerated”) at a desired incidence angle to the destination (e.g., acorrected incidence angle). In one embodiment, an incidence angle isdynamically corrected so that said optical signal beam is forwarded at arelatively shallow output angle. In one exemplary implementation, thedesired incidence angle is one that results in a shallow output angle.For example, the “regenerated” incidence angle (e.g., alpha) of theoptical signal beam strikes the next cascaded optical switch at an anglethat is close to zero. The optical signal beam is forwarded at a secondoutput angle (e.g., theta) that is relatively shallow and permits theoptical signal beam to travel on a path directed to an optical switchlocated in a relatively close proximity on the cascading optical switchfabric path.

In one exemplary implementation of the present invention, the opticalsignal beam is forwarded by an incidence corrective device that includesa fixed reflective component (e.g., a mirrored surface) oriented at aset angle (e.g., an angle defined by one half the output angle anoptical signal beam is forwarded from). In one exemplary implementationof the present invention, the optical signal beam is forwarded by anincidence corrective device that includes dynamically variable gratingbased optical switch ribbons deflected in a manner that propagates anoptical signal beam on a path that is normal to a cascaded secondoptical switch. In one embodiment of step 930, an optical signal beam isdirected by optical signal beam spread corrective process that correctsspread problems by refocusing the optical signal beam in a tighterpattern. For example, an optical signal beam is reflected by a concavesurface that corrects cumulative spread impacts on the optical signalbeam.

Thus, the present invention facilitates the inclusion of a number ofswitches in a cascaded device in a manner that facilitates efficientoptical signal switching. The present invention cascaded opticalswitching system and method facilitate minimization of cumulativedetrimental impacts associated with cumulatively increasingincidence/output angles and spreading of an optical signal beam. Apresent invention cascaded optical switching system “regenerates” anoptical signal beam path with a realigned or corrected incidence angle.In one embodiment of the present invention, the corrected incidenceangle facilitates shortening the cascading optical switch fabric length.Correcting the incidence angle also facilitates utilization of opticalswitches that are economical to manufacture, however, have limitedswitching range (e.g., switch with limited reflection or diffractionmovement). In one exemplary implementation, a present invention cascadedoptical switching system refocuses spreading optical signal beams andmitigates signal loss.

The foregoing descriptions of specific embodiments of the presentinvention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteaching. The embodiments were chosen and described in order to bestexplain the principles of the invention and its practical application,to thereby enable others skilled in the art to best utilize theinvention and various embodiments with various modifications as aresuited to the particular use contemplated. It is intended that the scopeof the invention be defined by the claims appended hereto and theirequivalents.

1. A cascaded optical switch system comprising: a plurality of cascadedoptical switches that form a cascaded optical switch fabric and directan optical signal beam from one of said plurality of cascaded opticalswitches to another of said plurality of cascaded optical switches in adifferent dimension while providing variable incidence angle correction;and an optical switch support member for supporting said plurality ofcascaded optical switches in a cascaded configuration that is compatiblewith directing said optical signal beam within the boundaries of saidcascaded optical switch fabric, said optical switch support membercoupled to said plurality of cascaded optical switches.
 2. The cascadedoptical switching system of claim 1 wherein said plurality of cascadedoptical switches include dynamically variable grating based opticalswitches for diffracting said optical signal beam, wherein saiddiffraction angle B is governed by the equation:B=Arcsin((m*Y/(n(w+s)))±Sin A), where B is the diffraction angle, A isan optical signal incidence angle, m is the order of the diffractionbeam, Y is the wavelength of the optical signal, n is the number ofribbons utilized in forming a single grating period, w is a ribbonwidth, and s is the space between ribbons.
 3. The cascaded opticalswitch system of claim 1 wherein said plurality of cascaded opticalswitches include grated light valve (GLV) switches.
 4. The cascadedoptical switch system of claim 1 wherein said multi-dimensionaldirectional device includes a reflective component.
 5. The cascadedoptical switch system of claim 4 wherein said multi-dimensionaldirectional device includes a diffractive component.
 6. The cascadedoptical switch system of claim 1 wherein said plurality of cascadedoptical switches are arranged in cascaded switching stages in which eachstage is located in a different dimension and include multiple cascadedoptical switches.
 7. The cascaded optical switch system of claim 1further comprising an optical signal beam spread mitigation device thatcorrects beam spreading by refocusing said optical signal beam.
 8. Acascaded optical switch system comprising: a plurality of cascadedoptical switches that form a cascaded optical switch fabric and directan optical signal from one of said plurality of cascaded opticalswitches to another of said plurality of cascaded optical switches in adifferent dimension; an optical switch support member for supportingsaid plurality of cascaded optical switches in a cascaded configurationthat is compatible with directing said optical signal within theboundaries of said cascaded optical switch fabric, said optical switchsupport member coupled to said plurality of cascaded optical switches;and an incidence corrective device for regenerating an optical signalpath with a realigned incidence angle, wherein said incidence correctivedevice includes a variable reflective component that reflectivelydiffracts an optical signal beam at different angles, said incidencecorrective device is coupled to said optical switch support member. 9.The cascaded optical switch system of claim 8 wherein said alignedincidence angle is a normal (zero) incidence angle.
 10. The cascadedoptical switch system of claim 8 wherein said incidence correctivedevice realigns said optical signal beam so that the incidence angle ofsaid optical signal beam strikes one of said plurality of cascadedoptical switches downstream in said cascaded optical switch fabric andproduces a relatively shallow output angle, wherein said relativelyshallow output angle directs said optical signal beam to one of saidplurality of cascaded optical switches downstream in said cascadedoptical switch fabric and said one of said plurality of cascaded opticalswitches is relatively close in accordance with said relatively shallowoutput angle to said incidence corrective device.
 11. The cascadedoptical switch system of claim 10 further comprising a multi-planedirectional device for directing said optical signal to a plane of saiddifferent dimension.
 12. The cascaded optical switch system of claim 10wherein said multi-plane directional device comprises a fixed reflectivesurface oriented at a particular angle to guide said optical signal beamto said different dimension.
 13. The cascaded optical switch system ofclaim 10 wherein said fixed reflective surface is a mirror oriented atless than 45 degrees.
 14. A cascaded optical switch system of claim 13further comprising an optical signal beam spread mitigation device thatcorrects beam spreading by refocusing said optical signal beam.
 15. Acascaded optical switching method comprising the steps of: receiving anoptical signal beam by cascaded optical switch fabric; propagating saidoptical signal beam along said optical switch fabric in differentdimensions; variably correcting an incidence angle; and forwarding saidoptical signal beam from said optical switch fabric.
 16. A cascadedoptical switching method of claim 15 further comprising combining twodimensional switching elements in a configuration that provides threedimensional switching.
 17. The cascaded optical switching method ofclaim 15 further comprising the steps of: receiving said optical signalbeam by an optical switch included in said cascaded optical switchfabric; and forwarding said optical signal beam from said optical switchincluded in said cascaded optical switch fabric.
 18. The cascadedoptical switching method of claim 17 wherein said optical signal beam isreceived by said optical switch at an incidence angle and isreflectively forwarded at a different output angle.
 19. The cascadedoptical switching method of claim 18 wherein said optical signal beam isforwarded to another optical switch included in said cascaded opticalswitch fabric at a relatively close location in accordance with acorrected shallow incidence angle.
 20. The cascaded optical switchingmethod of claim 15 further comprising correcting cumulative spreadimpacts on said optical signal beam.